Return flow carburetor



Feb. 19, 1963 T. M. BALL 3,078,077

RETURN FLow CARBURETOR Filed May 28, 1959 2 Sheets-Sheet 1y :Fl l.:l j!INVENTOR.

Taw/s 2% Ed/Z Feb. 19, 1963 T. M. BALL 3,078,077

RETURN FLow cARBURE'roR Filed May 28, 1959 2 Sheets-Sheet 2 l I 2? ;j 7/j 4 j! 4f if fi 4a f1 45 *1 3,978,077 L RnTURN FLGW CAREURETGR Thomas M.Ball, Bloomtield Hills, Mich., assigner to @hrysler Corporation,Highland Parli, Mich., a corporation of Delaware Filed P/iay 2h, 1959,Ser. No. $6,529 l2 Claims. (Cl. 251-36) This invention relates toimprovements in a carburetor particularly adapted for use with anautomobile internal combustion engine.

In conventional carburetors, a float controlled fuel inlet needle valveis employed to regulate the fuel level in the carburetor fuel bowl.Small dirt particles sometimes interfere with effective operation of thevalve, as for example by becoming lodged between mating valve seatswhich otherwise cooperate to regulate the fuel flow into the fuel bowl.Also the floats require considerable size in order to be effectivebecause of the comparatively low specific gravity of the fuel. lnconsequence the size of the fuel bowl must be appreciably larger than isotherwise desired.

.An important object of the present invention is to orovlde an improvedcarburetor which avoids the foregoing objections and in particular toprovide a iloatless carburetor which does not require a fuel inletneedle valve.

Another object is to provide such a construction including overilowstaudpipe in the fuel bowl having an upper opening which determines themaximum fuel level in the bowl. A fuel inlet pump is provil ed to pumpfuel into the bowl at a rate in excess of demand. The excess fueloverilows into the standpipe and is returned to the fuel tank, ln orderto overcome adverse grade conditions which prevent the excess fuel fromreturning to the tank by gravity flow, a scavenging pump is provided inthe fuel return line between the overflow standpipe and the tank.

Among other advantages of the above structure, elimination of thenecessarily large iloat enables utilization of a comparatively smallfuel bowl closely adjacent the inlet air induction conduits of amultiple barrel carburetor, for example. 'l he small fuel bowl thuslocated is less sensitive to grade and inertial edects and enablesuniform fuel distribution to each of the several induction conduits.Also recirculation of the fuel drives off its more volatile fuelfractions and thereby minimizes some of the problems of the conventionalfloat controlled carburetor, as for example those concerned with vaporformation.

ln order to provide adequate fuel during maximum engine speed at wideopen throttle, a fuel inlet pump is provided which delivers an excesssupply of fuel to the fuel bowl during all operating conditions of theengine. When the throttle is suddenly closed while the engine is stilloperating at high speed, unless some provision is made to the contrary,approximately 98% of the fuel supplied to the fuel bowl will berecirculated, whereas approximately only 2% of the fuel will be used bythe engine. ln general the life of a fuel pump and in particular thelife of an engine driven diaphragm type pump, which is preferred forsupplying fuel in the quantity required and at a substantially uniformpressure regardless of changes in engine speed, depends upon thequantity of fuel pumped.

For the above reasons, as well as the desirability of conserving powerin an automobile engine and of minimizing fuel heating by excessiverecirculation, another object of the present invention is to provideimproved simple and highly effective means for supplying fuel to thefuel bowl in reasonable and safe amounts related to engine requirements.

Another object is to provide an adjustable inlet control valve in thefuel inlet conduit to the fuel bowl and to adjust this Valve in responseto variations in engine load.

Patented Feb. i9, 1h53 Other and more speciiic objects are to adiust theinlet control valve by a direct linkage with the throttle actuatingmechanism, or by pressure actuated means connected with the engine airinlet induction system or with the discharge side of the scavengingpump.

Other objects of this invention will appear in the following descriptionand appended claims, reference being had to the accompanying drawingsforming a part of this specication wherein like reference charactersdesignate corresponding parts in the several views.

FIGURE l is a schematic mid-sectional view of a return dow carburetorand pump embodying the present invention.

FIGURE 2 is a view similar to FlGURE l illustrating a modification.

FIGURE 3 is a view similar to FIGURE l illustrating anothermodification.

FIGURE 4 is a view similar to FlGURE l illustrating still anothermodification.

lt is to be understood that the invention is not limited in itsapplication to the details of construction and arrangemen of partsillustrated in the accompanying drawings, since the invention is capableof other embodiments and of being practiced or carried out in variousways. Also it is to be understood that the phraseology or terminologyemployed herein is for the purpose of description and not of limitation.

Referring to HEURE l, the carburetor shown comprises a cast housingformed to provide an air inlet induction conduit including a venturiportion lll having a restricted venturi lll at its upper portion and athrottle blade l2 pivotally mounted on a shaft i3 at a lower portionusually referred to as the throttle body. An upper portion of thecasting is formed to provide an air horn i4 adapted to be connected withthe usual air llter and opening at its downstream end into the venturill to supply air thereto. The casting portions lil and ld are suitablysecured together, as for example by screws not shown, and comprise anupper portion of the air inlet and fuel mixing induction system whichextends down stream of the throttle valve l?. and discharges into theusual engine cylinders in a conventional manner.

Integral with the casting lo in the present instance is a fuel bowlcasting l5 containing an annular chamber or fuel bowl 16 enclosing acylindrical standpipe or weir 17 which also serves as an accelerationpump cylinder containing a plunger 18 reciprocable in its lower portionand secured to a plunger shaft i9 for actuation thereby. Where desiredthe shaft 19 is connected by suitable linkage with a pedal operatedaccelerator mechanism which controls the opening and closing of valve l2to operate conjointly therewith. Upon upward movement of plunger 18,fuel is drawn into the lower portion of chamber 17 via conduit 20 incommunication with the bowl lo. A suitable check va-lve illustratedschematically as a ball check element 2l normally seats at the mouth ofthe duct 2li opening into the lower portion of chamber i7 to preventloss of fuel therefrom but is raised from its seat by the fuel ilow intochamber 17 on the upstroke of plunger 13. Upon downward movement ofplunger i8 the fuel is forced from chamber 17 into the induction conduitvia acceleration fuel conduit 22, ball check valve 23, and nozzle 24which latter discharges into the induction conduit at a locationimmediately above the throat of venturi l1. The check valve 23 isschematically illustrated as a ball normally urged by aspring to aseated position closing nozzle 24 from the interior of chamber 17, theball being readily movable upward against the tension of its seatingspring by the acceleration fuel pressure upon downward movement ofplunger lll. The main fuel to the engine is supplied via duct 25 whichopens at its lower end through metering port 2o into the fuel bowl 16and maintains the fuel in the bowl 16 at a predeterminedA maximum leveldetermined by the effective height of the standpipe 17 without recourseto a float operated mechanism. Fuel is supplied to the bowl 16 from asuitable fuel tank via conduit 28 having a valving orifice 29 therein. Atapered valve element 30 below or upstream of orice 29 is connected by astem 31 to the underside of a flexible diaphragm 32 for controlling thefuel flow through orifice 29. Thus upon upward movement of valve 30,orice 29 is progressively restricted to reduce the fuel flowtherethrough provided that the fuel supply pressure upstream of orifice29 remains substantially constant, as described below.

The diaphragm 32 is confined within a pressure chamber 33 and partitionsthe latter into upper and lower parts. A coil spring 34 in the upperchamber part under compression between diaphragm 32 and housing 33normally urges diaphragm 32 with the connected stem 31 and valve 30downwardly to maintain orifice 29 open. The chamber part above diaphragm32 is connected by a pressure duct 35 to the induction conduit at apoint adjacent and downstream of the throttle valve 12. In order tofacilitate operation of the diaphragm 32, the lower chamber part belowthe diaphragm is vented at 36 to the atmosphere.

A multiple piece fuel pump housing 37 comprising an upper dome 38 and alower basin 39 cooperate with diaphragms 40 and 41 respectively toprovide an inlet fuel pumping or working chamber 42 and an exhaust fuelpumping or scavenging chamber 43. Springs 44 and 45 under compressionbetween portions of housing 37 and diaphragms 40 and 41 respectivelyurge the former diaphragm upwardly and the latter diaphragm downwardlyto effect the pumping strokes for the respective chambers 42 and 43.

The upper working chamber 42 comprises a portion of supply duct 28 whichcommunicates upstream of chamber 42 with the fuel tank. Fuel enters andleaves charnber 42 via an inlet port 46 and a discharge port 47associated with check valves 48 and 49 respectively. Upon downwardmovement of diaphragm 40 as explained below, fuel is drawn in thedirection of the arrow 28a from the tank and through inlet port 46 intoworking chamber 42. During this operation ball valve 48 is forced fromits seat at port 46 by the fuel ow, andball valve 49 seats at thedischarge port 47 to close the latter from the fuel bowl 16. Upon upwardmovement of diaphragm 40, ball valve 48 is caused to seat at port 46 toclose the working chamber 42 from the fuel tank. During this operation,the pressure exerted in chamber 42 unseats ball valve 49 from port 47and supplies fuel via conduit 28 and orifice 29 to the fuel bowl 16 inaccordance with the setting of valve 30. The spaces at the sides of thediaphragms 40 and 41 opposite chambers 42 and 43 respectively are ventedto the atmosphere by ducts 50 and 51 to facilitate the pump operation.

Fuel is returned in the direction of arrow 52a from standpipe 17 to thefuel tank via fuel return conduit 52 which includes chamber 43 as aportion thereof. Upstream, the conduit 52 communicates with standpipe 17at a location above the uppermost limit of movement of plunger 18. Thereturn fuel enters chamber 43 via port 53 and discharges from chamber 43via port 54. Ball check valves and A56 are associated with ports 53 and54 respectively, so that upon upward movement of diaphragm 41 asdescribed below, ball 56 seats against port 54 to close chamber 43 fromthe fuel tank. During this operation, ball 55 is unseated from port- 53to open communication between chamber 43 and standpipe 17 and to drawfuel from the latter. Upon downward movement of diaphragm 41, ball 55 isseated against port 53 to close chamber 43 from standpipe 1.7.Simultaneously ball 56 is unseated from port 54 by the pressure inchamber 43 to discharge fuel from the latter in the direction of arrow52a to the tank. Movement limiting pins in the conduits 28 and 52associated with the ball valves 43, 49, 55 and 56 prevent undue movementof the balls from their associated ports. Inasmuch as the check valvesare well known, these are merely shown schematically and are notdiscussed in further detail.

Aetuation of the diaphragms 40 and 41 is accomplished by driving shafts57 and 58 connected to these diaphragms and terminating -in enlargedheads 59 and 6i? respectively. Pivotal levers 61 and 62 are pivoted onhousing 37 at locations 63 and 64 respectively between their ends. Eachlever has one end engaged with a rotating eccentric cam mounted on ashaft 66 driven by the automobile engine. The opposite ends of thelevers 61 and 62 are provided with oversized openings 67 and 68 throughwhich the rods 57 and 58 extend freely to enable their relative slidingmovement with respect to the levers 61 and 62 until the levers engagethe enlarged head-s 59 and 60.

Upon operation of the automobile engine, shaft 66 is rotated to turneccentric cam 65 and thereby cause pivoting of levers 61 and 62. Uponclockwise pivoting of lever 61, or counterclockwise pivoting of lever62, the head 59 or 60 is engaged to pull the associated rod 57 or 58 inthe direction to compress the spring 44 or 45 as the case might be. Uponcounterclockwise pivoting of lever 61 and clockwise pivoting of lever62, the oversized openings 67 and 68 enable the levers to swing independently of the shafts 57 and 58, whereupon springs 44 and 45 arereleased to force diaphragms 42 and 43 in pumping actions toward theassociated dome 38 or basin 39. The pivotal action of levers 61 and 62merely compresses the springs 44 and 45 alternately, which latter thenexert resilient :force to effect the pumping action of the associateddiaphragms 40 and 41. In consequence, fuel is discharged from chamber 42at a uniform optimum pressure determined by the force of spring 44. Uponthe upward spring urged pumping stroke of `diaphragm 40, fuel isdischarged via port 47 toward valve control orifice 29 and through thelatter as aforesaid to fuel `bowl 16. All fuel in excess of enginerequirements overflows the standpipe 17 and returns by conduit 52 tochamber 43 via port 53, whereupon the fuel is pumped to the fuel tank bydownward spring urged pumping movement of diaphragm 41.

Variations in engine fuel requirements are detected by conduit 35 whichprogressively increases the pressure in chamber 33 above diaphragm 32 asvalve 12 is pivoted toward a wide open position, i.e., as engine loadincreases. The increased pressure in chamber 33, in cooperation withspring 34, urges diaphragm 32 and valve stem 31 downward, therebycausing valve 30 to decrease the restriction at orifice 29. Inconsequence increased fuel ow through orifice 29 is enabled withincreasing engine load. During the converse action, as valve 12 movestoward its closed position shown, the pressure below the throttle valveand accordingly the pressure in chamber 33 above diaphragm 32 decreases,enabling at mospheric pressure on the underside of diaphragm 32 to lurgethe latter upward against the tension of spring 34Vand cause restrictionof orifice 29 by valve 30. Thus with decreasing engine load, the fuelflow to bowl 16 is decreased and recirculation of fuel supplied theretois minimized.

Although the structure of FIGURE 1 provides means for supplying fuel tobowl 16 at a rate which is a function of engine load, the vacuum inducedforce below valve 12 is at its maximum at low engine load andprogressively decreases as engine load increases. Accordingly', atcomparatively high engine load when the throttle valve 12 is pen fullyor nearly so, the vacuum.

force acting on diaphragm 32 is a minimum and changes in the throttleposition result in comparatively W magnitude pressure changes ondiaphragm 32.

Where increased edectiveness of the vacuum induced force at `high engineload is desired, a construction such as illustrated in FIGURE 2 ispreferred. The general arrangement of the return flow carburetor andpump is the same in FIGURE 2 as in FIGURE 1 so that identical parts arenumbered the same in both drawings. The distinction of FIGURE 2 is thatconduit 35 is replaced by conduit 69, and valve 30 is replaced by atapered valve 79 at the upstream side of orice 29. Conduit 69 connectschamber 33 above diaphragm 32 with the induction conduit at a locationadjacent the throat of the venturi il. Accordingly as engine loadincreases, the vacuum induced force at the throat of venturi 1lincreases and becomes a maximum at wide open throttle. The resulting lowpressure above diaphragm 32 enables the atmospheric pressure on theunderside of the diaphragm to urge the latter upwardly against the forceof spring 34 and move valve 7u away from orifice 29 to reduce therestriction thereof. In consequence, as the airliow through venturithroat ll increases with increasing engine load, the fuel flow throughorifice 29 into bowl lo increases. Conversely as airllow through venturithroat ll decreases with decreasing engine load, the vacuum inducedforce above diaphragm 32 decreases, enabling spring 3dto move valve 7udownwardly and increase the restriction at orifice 29, thereby reducingthe fuel flow into bowl i6. In the FlGURE 2 construction, the vacuuminduced force at the throat of venturi 11 becomes a minimum at lowengine load. Accordingly where desired a dual control of the inlet fuelow as illustrated in both FIGURES l and 2 may be employed to assureadequate operating force during conditions of both high and low engineloads.

IGURE 3 also illustrates a return flow carburetor and pump as in FIGURESl and 2 wherein corresponding parts are numbered the same. In FIGURE 3,valve 71 replaces valve 3@ of FIGURE l, and spring 72 replaces spring34. Also in FIGURE 3, instead of employing the induction conduitpressure to control the restriction of orice 29 in accordance withengine load, a conduit 73 connects the upper portion of chamber 33 abovediaphragm 32 with the return flow conduit 52 at a location downstream ofpumping chamber d3, thereby to regulate the pressure above diaphragm 32as a function of the return fuel flow. In order to accentuate thepressure changes in conduit '73, a restriction '74 is provided inconduit 52 at a location downstream of the latters connection withconduit 73.

In accordance with the structure of FIGURE 3, when engine load and fuelconsumption drop, the return flow through conduit 52 will normally tendto increase. The increased return fuel flow is indicated by an increasedpressure in the portion of conduit 52 between pumping chamber 43 andrestriction 74. This pressure increase is transmitted by conduit 73 todiaphragm 32 to urge the latter downwardly and cause valve 71 toprogressively restrict orice 29 and reduce the fuel flow to bowl 16.Accordingly recirculation of fuel through the pumping mechanism will bedecreased until the fuel yflow into bowl lr6 reaches an equilibriumcondition determined by the new engine load requirement.

It is also apparent that upon an increase in fuel consumption by theengine, the fuel return flow in conduit 52 will decrease and thepressure in conduit 73 acting on the upper side of diaphragm 32' willlikewise decrease, enabling spring 72 to urge diaphragm 3K2 upwardly andprogressively decrease the restriction at orifice 29; creased fuel flowto bowl 16 is thus enabled until the system again reaches the desiredequilibrium condition determined by the fuel requirements at the newengine load. The foregoing structure is independent of pressure changesin the induction conduit and depends only upon the rate of return fuelflow in conduit S2, which is thus regulated toa desired nominal valueduring all conditions of engine operation so as to prevent excessiverecirculation of fuel by the pumping mechanism.

FIGURE 4 illustrates the return flow carburetor and pumping mechanism asin FIGURE 1 wherein corresponding parts are again numbered the same. InFIG- URE 4 however, instead of controlling the restriction of fuel inletorifice 29 by induction conduit pressure as in FIGURES 1 and 2, or byreturn flow fuel pressure as in FIGURE 3, the restriction to orifice 29is controlled by a mechanical linkage with the accelerator mechanism.Pressure chamber 33 is replaced by housing 7S, and valve 3u of FIGURE 1is replaced by a similar conically tapered valve 76 at the upstream sideof orifice 29'.

A valve actuating stem 77 secured to valve 7 d extends upwardlytherefrom and through housing 75 and is yieldcingly urged downwardly bya coil spring 78 under compression around stem 77 between `a portion ofhousing 75 `and a spring retaining seat 79 suitably secured to stem '77.The latter extends upwardly and is freely slidable through an oversizedhole Sti in a dog-leg bracket S1 and terminates in an enlarged head 82which is unable to pass through opening 80. Bracket 811 is secured tothe upper horizontal portion of a dog-leg lever 83 having a verticaldepending portion. A connecting link d4 is pivotally connected at S5 tothe lower depending portion of lever 83 and is also pivotally connectedat 86 lto the outer swinging end of `a crankarm 37 which in turn iskeyed to an extension of valve shaft 13 exteriorly of the inductionconduit l0.

Upon pivoting of crankarm 87 as for example by linkage 88 which may besuitably connected with the customary pedal operated throttle mechanism,valve 12 is opened or closed. Upon clockwise pivoting of crankarm 87,throttle valve l2 is progressively opened and lever 813 is moveddownwardly, causing bracket Si to slide downwardly freely along valvestem 77 4and enabling spring 78 to force stem 77 and valve 76 downwardlyto decrease the restric-tion at orifice 29: In consequence upon openingof throttle valve 12 during increased engine load, fuel ow throughorifice 29 to bowl 16 is increased. Upon counterclockwise or closingmovement of valve l2 with decreasing engine load, lever 83 is movedupwardly. Bracket 81 then engages the enlarged head 82 and raises stem77 against the force of spring 7S, thereby causing tapered valve 76 toprogressively restrict orifice 29 and reduce the fuel ow to bowl 16.

Having thus described my invention, I claim:

l. In a floatless carburetor for an internal combustion engine having anintake manifold system, a fuel bowl, inlet conduit means for connectingsaid bowl with a source of pressurized fuel, means for maintaining thefuel in said bowl at a predetermined level comprising an overflow weirin said bowl defining at least in part a chamber adapted to receiveexcess fuel overflowing said weir from said bowl when the fuel in saidbowl attains said predetermined level, fuel return means incommunication with said chamber to drain fuel therefrom upon overflow ofexcess fuel from said bowl into said chamber, valve means in saidconduit means at a location between said source and bowl for controllingfuel ow in said conduit means, a pressure chamber, a pressure actuatedmovable element in said pressure chamber, means operably connecting saidpressure chamber with said intake manifold system to vary the pressurein said pressure chamber and thereby to actuate said element inaccordance with changes in engine load, and means operably connectingsaid element with said valve means for adjusting the latter in4accordance with said changes in engine load to increase the fuel flowin said conduit means with increasing engine load.

2. ln a floatless carburetor for an internal combustion engine having anintake manifold system, a throttle valve -in said system, a fuel bowl,inlet conduit means for connecting said bowl with a source ofpressurized fuel, means for maintaining the fuel in said bowl at apredetermined level comprising an ovrflow weir in said bowl defining atleast in part a chamber adapted to receive excess fuel overflowing saidweir from said bowl when the fuel in said bowl attains saidpredetermined level, fuel return means in communication with saidchamber to drain fuel therefrom upon overflow of excess fuel from saidbowl into said chamber, valve means in said conduit means at a locationbetween said source and bowl for controlling fuel flow in said conduitmeans, a pressure chamber, a pressure actuated movable element in saidpressure chamber, duct means connecting said pressure chamber with saidintake manifold system at a location adjacent and downstream of saidthrottle valve to vary the pressure in said pressure chamber and therebyto -actuate said element in accordance with pressure changes in saidintake manifold system, and means operably connecting said element withsaid valve means for adjusting the latter in accordance with pressurechanges in said intake manifold system.

3. In a floatless carburetor for an internal combustion engine having anintake manifold system, a venturi in said system, a fuel bowl, inletconduit means for connecting said bowl with a source of pressurizedfuel, means for maintaining the fuel in said bowl at a predeterminedlevel comprising an overflow Weir in said bowl defining at least in parta chamber adapted to receive excess fuel overflowing said Weir from saidbowl when the fuel in said bowl attains said predetermined level, fuelreturn means in communication with said chamber to drain fuel therefromupon overflow of excess fuel from said bowl into said chamber, valvemeans in said conduit means at a location between said source and bowlfor controlling fuel flow in said conduit means, a pressure chamber, apressure actuated movable element in said pressure chamber, duct meansconnecting said pressure chamber with said intake manifold system at alocation adjacent the throat of said venturi to vary the pressure insaid pressure chamber and thereby to actuate said element in accordancewith pressure changes in said intake manifold system, and meansroperablyconnecting said element with said valve means for adjusting the latterto increase the fuel flow in said conduit means with increasing engineload.

4. In a floatless carburetor for an internal combustion engine having anintake manifold system, a throttle valve in said system, a fuel bowl,inlet conduit means for connecting said bowl with a source ofpressurized fuel, means for maintaining the fuel in said bowl at apredetermined level comprising an overflow Weir in said bowl defining atleast in part a chamber adapted to receive excess fuel overflowing saidweir from said bowl when the fuel in said bowl attains saidpredetermined level, fuel return means in communication with saidchamber to drain fuel therefrom upon overflow of excess fuel from saidbowl into said chamber, valve means in said conduit means at a locationbetween said source and bowl for controlling fuel flow in said conduitmeans, and means responsive to intake manifold pressure for adjustingsaid valve means comprising a pressure chamber, a flexible diaphragmcomprising a wall of said pressure chamber, duct means connecting saidpressure chamber with said intake manifold system at a location adjacentand downstream of said throttle valve, the low pressure at said locationwhen said throttle valve approaches a closed position being effective tomove said diaphragm in one direction, resilient means opposing movementof said diaphragm in said one direction, and means operably connectingsaid diaphragm and valve means for actuating the latter to decrease thefuel flow in said conduit means progressively with progressive movementof said diaphragm in said one direction.

5. In a floatless carburetor for an internal combustion f engine havingan intake manifold system, a venturi in said system, a fuel bowl, inletconduit means for connecting said bowl with a source of pressurizedfuel, means for maintaining the fuel in said bowl at a predeterminedlevel comprising an overflow Weir in said bowl defining at least in parta chamber adapted to receive excess fuel overflowing said weir from saidbowl when the fuel in said bowl attains said predetermined level, fuelreturn means in communication with said chamber to drain fuel therefromupon overflow of excess fuel from said bowl into said chamber, valvemeans in said conduit means ata location between said source and bowlfor controlling fuel flow in said conduit means, and means responsive toengine load for adjusting said valve means comprising a pressurechamber, a flexible diaphragm comprising a wall of said pressurechamber, duct means connecting said pressure chamber with said intakemanifold system at a location adjacent the throat of said venturi, thelow pressure at said location being effective to move said diaphragm inone direction, resilient means opposing movement of said diaphragm insaid one direction, and means operably connecting said diaphragm andvalve means for actuating the latter to increase the fuel flow in saidconduit means progressively with progressive movement of said diaphragmin said one direction.

6. ln a floatless carburetor for an internal combustion engine, a fuelbowl, inlet conduit means for connecting said bowl with a source ofpressurized fuel, means for maintaining the fuel in said bowl at apredetermined level comprising an overflow weir in said bowl defining atleast in part a chamber adapted to receive excess fuel overflowing saidweir from said bowl when the fuel in said bowl attains saidpredetermined level, fuel return means in communication with saidchamber to drain fuel therefrom upon overflow of excess fuel from saidbowl into said chamber, valve means in said conduit means forcontrolling fuel flow in the latter, said fuel return means includingpumping means for pumping the excess fuel from said chamber, and meansresponsive to the output of said pumping means for adjusting said valvemeans.

7. In a floatless carburetor for an internal combustion engine, a fuelbowl, inlet conduit means for connecting said bowl with a source ofpressurized fuel, means for maintaining the fuel in said bowl at apredetermined level comprising an overflow Weir in said bowl defining atleast in part a chamber adapted to receive excess fuel overflowing saidweir from said bowl when the fuel in said bowl attains saidpredetermined level, fuel return means in communication with saidchamber to drain fuel therefrom upon overflow of` excess fuel from saidbowl into said chamber, valve means in said conduit means forcontrolling fuel flow in the latter, said fuel return means includingpumping means for pumping the excess fuel from said chamber, and meansresponsive to the output of said pumping means for adjusting said valvemeans to decrease the fuel flow in said conduit means progressively withincreasing output from said pumping means.

8, In a floatless carburetor for an internal combustion engine, a fuelbowl, inlet conduit means for connecting said bowl with a source ofpressurized fuel, means for maintaining the fuel in said bowl at apredetermined level comprising an overflow Weir in said bowl defining atleast in part a chamber adapted to receive excess fuel overflowing saidweir from said bowl when the fuel in said bowl attains saidpredetermined level, fuel return means in communication with saidchamber to drain fuel therefrom upon overflow of excess fuel from saidbowl into said chamber, valve means in said conduit means forcontrolling fuel flow in the latter, said fuel return means includingpumping means for pumping the excess fuel from said chamber, meansrestricting the discharge fuel flow from said pumping means to effect apressure differential across the restricting means, and means responsiveto said pressure differential for adjusting said valve means.

9. In a floatless carburetor for an internal combustion engine, a fuelbowl, inlet conduit means for connecting said bowl with a source ofpressurized fuel, means for maintaining the fuel in said bowl at apredetermined level comprising an overflow wcir in said bowl defining atleast in part a chamber adapted to receive excess fuel overflowing saidWeir from said bowl when the fuel in said bowl attains saidpredetermined level, fuel return means in communication with saidchamber to drain fuel therefrom upon overflow of excess fuel from saidbowl into said chamber, valve means ni said conduit means forcontrolling fuel ow in the latter, said fuel return menas includingpumping means for pumping the excess fuel from said chamber, meansresponsive to the output of said pumping means for adjusting said valvemeans comprising a pressure chamber, a movable element in said chamberactuated by the pressure therein, means operably connecting said chamberwith the discharge side of said pumping means to vary the pressure insaid chamber, and means operably connecting said element with said valvemeans for adjusting the latter in accordance with changes in the outputof said pumping means.

10. In a oatless carburetor for an internal combustion engine, a fuelbowl, inlet conduit means for con necting said bowl with a source ofpressurized fuel, means for maintaining the fuel in said bowl at apredetermined level comprising an overow Weir in said bowl defining atleast in part a chamber adapted to receive excess fue] overflowing saidweir from said bowl when the fuel in said bowl attains saidpredetermined level, fuel return means in communication with saidchamber to drain fuel therefrom upon overiiow of excess fuel from saidbowl into said chamber, valve means in said conduit means forcontrolling fuel ow in the latter, said fuel return means includingpumping means for pumping the excess fuel from said chamber, meansresponsive to the output of said pumping means for adjusting said valvemeans comprising a pressure chamber, a movable element in said chamberactuated by the pressure therein, means operably connecting said chamberwith the discharge side of said pumping means to vary the pressure insaid chamber, and means operably connecting said element with said valvemeans for adjusting the latter in yaccordance with changes in the outputof said pumping means to decrease the fuel flow in said conduit meansprogressively with progressively increasing output from said pumpingmeans.

ll. In a iloatless carburetor for an internal combustion engine, a fuelbowl, inlet conduit means for connecting said bowl with a source ofpressurized fuel, means for maintaining the fuel in said bowl at apredetermined level comprising an overow weir in said bowl deiining atleast in part a chamber adapted to receive excess fuel overflowing saidweir from said bowl when the fuel in said bowl attains saidpredetermined level, fuel return means in communication with saidchamber to drain fuel therefrom upon overow of excess fuel from saidbowl into said chamber, valve means in said conduit means forcontrolling fuel flow in the latter, Said fuel return means includingpumping means for pumping the excess fuel from said chamber, meansresponsive to the output of said pumping means for adjusting said valvemeans comprising a pressure chamber, a flexible diaphragm comprising awall of said chamber, duct means connecting said chamber with the outputside of said pumping means, the output pressure of said pumping meansbeing effective to move said diaphragm in one direction, resilient meansopposing movement of said diaphragm in said one direction, and meansoperably connecting said diaphragm and valve means for actuating thelatter to decrease the fuel flow in said conduit means progressivelywith progressive movement of said diaphragm in said one direction.

l2. In a floatless carburetor for an internal combustion engine, a fuelbowl, inlet conduit means for connecting said bowl with a source ofpressurized fuel, means for maintaining the fuel in said bowl at apredetermined level comprising an overow Weir in said bowl defining atleast in part a chamber adapted to receive excess fuel overflowing saidweir from said bowl when the fuel in said bowl attains saidpredetermined level, fuel return means in communication with saidchamber to drain fuel therefrom upon overflow of excess fuel from saidbowl into said chamber, valve means in said conduit means forcontrolling fuel iiow in the latter, said fuel return means includingpumping means for pumping the excess fuel from said chamber, meansresponsive to the output of said pumping means for adjusting said valvemeans comprising a restriction in the output side of said pumping meansto eifect a back pressure upstream of said restriction, a pressurechamber, a flexible diaphragm comprising a wall of said chamber, ductmeans connecting said chamber with the output side of said pumping meansat a location upstream of said restriction, said back pressure beingeffective to move said diaphragm in one direction, resilient meansopposing movement of said diaphragm in said one direction, and meansoperably connecting said diaphragm and valve means for actuating thelatter to decrease the fuel iiow in said conduit means progressivelywith progressive movement of said diaphragm in said one direction.

References Cited in the tile of this patent UNITED STATES PATENTS1,881,860 Muzzy Oct. l1, 1932 2,136,959 Winfield NOV. 15, 1938 2,254,850Mallory Sept. 2, 1941 2,454,974 Mennesson Nov. 30, 1948 2,691,509Rivoche Oct. 12, 1954 2,846,203 Voss et al Aug. 5, 1958 2,905,455Eberhardt Sept. 22, 1959

1. IN A FLOATLESS CARBURETOR FOR AN INTERNAL COMBUSTION ENGINE HAVING AN INTAKE MANIFOLD SYSTEM, A FUEL BOWL, INLET CONDUIT MEANS FOR CONNECTING SAID BOWL WITH A SOURCE OF PRESSURIZED FUEL, MEANS FOR MAINTAINING THE FUEL IN SAID BOWL AT A PREDETERMINED LEVEL COMPRISING AN OVERFLOW WEIR IN SAID BOWL DEFINING AT LEAST IN PART A CHAMBER ADAPTED TO RECEIVE EXCESS FUEL OVERFLOWING SAID WEIR FROM SAID BOWL WHEN THE FUEL IN SAID BOWL ATTAINS SAID PREDETERMINED LEVEL, FUEL RETURN MEANS IN COMMUNICATION WITH SAID CHAMBER TO DRAIN FUEL THEREFROM UPON OVERFLOW OF EXCESS FUEL FROM SAID BOWL INTO SAID CHAMBER, VALVE MEANS IN SAID CONDUIT MEANS AT A LOCATION BETWEEN SAID SOURCE AND BOWL FOR CONTROLLING FUEL FLOW IN SAID CONDUIT MEANS, A PRESSURE CHAMBER, A PRESSURE ACTUATED MOVABLE ELEMENT IN SAID PRESSURE CHAMBER, MEANS OPERABLY CONNECT- 